PROJECT SUMMARY The ability of mesenchymal stromal cells (MSCs) to adapt to their tissue niche and remodel extracellular matrix (ECM) could be therapeutically beneficial in treating fibrotic diseases. However, leveraging this property has been challenging because MSCs are rapidly cleared from tissue once delivered. Thus, specific pathways to induce MSCs to remodel the ECM and the utility of these remain unclear. We described herein a highly efficient approach to encapsulate single cells in engineered microgels with predefined biochemical and biophysical cues. We have fine-tuned this approach to show that clearance of MSCs is significantly delayed when they are delivered in thin microgels intratracheally to lungs. Importantly, our preliminary data show that this treatment decreases collagen accumulation in a murine lung fibrosis model. We show in these supporting studies amplified ability of MSCs to degrade collagen-I when the cells are encapsulated in engineered hydrogels with tunable stiffness. In this my first RO1 proposal, I will build upon these results to test the hypothesis that programming of MSCs using specifically engineered microgels activates the potential of MSCs to promote resolution of fibrosis and thus restore lung function. In Aim 1, we will determine the role of microencapsulation in controlling retention of MSCs in lungs and facilitating resolution of lung fibrosis. In Aim 2, we will determine the potentially important role of the inflammatory cytokine tumor necrosis factor-? (TNF?) in modifying the phenotype of microencapsulated MSCs to produce high amounts collagenases with enhanced potential to resolve lung fibrosis. We predict that selectively activating TNF receptor 2 in MSCs encapsulated in soft microgels can resolve lung fibrosis. The project is highly multidisciplinary in that it will employ a combination of expertise in biomaterials, lung fibrosis, biophysical, genetic, and mouse in vivo approaches to address the specific aims. The results will help to define how MSCs can facilitate resolution of fibrosis through prolonging their in vivo residence time in lungs, and modifying their phenotype through encapsulation in engineered and tunable microgels to optimize their production of collagenases. We thus hope to develop novel MSC based approaches to remodel aberrant extracellular matrix and to treat lung fibrosis. !